In recent years, the development of automobile technology has made engine sound and the like reduced. As a result, small noise in the car has caused to be anxious. Although there are multiple noise generation sources, the present invention is to reduce a noise generated by rubbing plastic materials constituting a seat portion of a seat with each other.
Generally, a seat for an automobile (hereinafter, referred to as a seat) includes a backrest portion with which a back of a driver's body is in contact to support the body from behind, and a seat portion with which a hip and a thigh are in contact to support the body from below. It is known that the seat portion includes a seat core member formed of a relatively hard material for maintaining the shape of the seat portion, and a cushion layer covering the seat core member and formed of a relatively soft material functioning as a cushioning member between the body and the seat core member.
A technique for forming a seat by using a soft urethane-based resin foam as a cushion layer and a thermoplastic resin foam such as a hard urethane-base resin foam or a polystyrene-base resin foam as a seat core member, and covering the seat core member with the cushion layer is known as a seat structure for the automobile.
This technique is disclosed in, for example, Patent Documents 1 and 2.
In Patent Document 1, a structure and a material of a seat cushion member 1 are proposed in which a soft polyurethane foam layer 2 covers a core member 3 made of a polyolefin resin foam. The seat illustrated in the document is a seat integrally formed with a backrest portion substantially perpendicular to a horizontal seat portion of the seat, and includes a cushion layer for imparting a seating comfort when a passenger sits on, and a seat core member which is under the cushion layer and responsible for structural strength and rigidity required for the seat.
In Patent Document 2, a problem is pointed out as “in a case of a horizontal seat, if a body of a passenger is not properly fixed with the seat belt, when a pelvis of the passenger sitting moves forward and downward by a collision, there is a possibility that the seat belt is entangled with the body of the passenger to be a fatal accident”. In order to prevent this, “an anti-submarine seat having a structure in which a relatively hard polyurethane foam is covered by a relatively soft polyurethane foam, and a structure that prevents the passenger from slipping off the seat in the event of an accident by making a seat surface rise forward or hardening a front end” is proposed.
On the other hand, in the structures as described above, there are techniques disclosed in the following Patent Documents 3 and 4 with respect to noise countermeasures generated by rubbing of other members with each other.
Patent Document 3 describes a current situation that “in an interior material made of a foam mold body of an automobile, the interior material having a flat surface is used in consideration of ease of cleaning and the like” and a problem that “during running of the vehicle or the like, a vehicle structure and the interior material, for example, a tool box mounted on the vehicle, in contact therewith rub against each other due to vibration or the like, which may cause abnormal noise”. As a solution to the problem, “a foam mold body molded by heating expandable resin particles filled in a foam molding mold, provided with a plurality of first ridges aligned in one direction and a plurality of second ridges aligned in the other direction and arranged to intersect with the first ridges on the surface, and in which the cross sections of the first ridge and the second ridge each is tapered to a tip end side” is proposed.
In addition, Patent Document 4 describes problems that: “relating to the automobile, reducing noise has become a problem for many years. Specifically, reduction of squeaking noise is a problem. Focusing on noise caused by a plastic foam product, squeaking noise is caused by friction between the plastic foam product and another automobile component. The cause of the friction is periodic shaking, vibration, bending or twisting of the automobile”. As a solution to the problems, “a plastic foam product that is formed from beads and is provided with spherical, conical protrusions formed so as to minimize noise due to the friction on the surface of the beads” is proposed.